This invention is directed to lighting systems, and in particular, to light emitting diodes (LED) pump light with multiple phosphors.
Solid state lighting is known. Solid state lighting relies upon semiconductor materials to produce light, e.g. by light emitting diodes. Red LEDs are known and use Aluminum Indium Gallium Phosphide or AlInGaP semiconductor materials, among others. Most recently, Shuji Nakamura pioneered the use of InGaN materials to produce LEDs emitting blue light. The blue LEDs led to other innovations such as solid state white lighting and the blue laser diode.
High intensity UV, blue, and green LEDs based upon the InGaN material system have been proposed and demonstrated. Efficiencies have typically been highest in the UV-violet, but drop off as the emission wavelength is increased to blue or green. Unfortunately, achieving high intensity, high-efficiency InGaN-based green LEDs has been problematic. Additionally, InGaN-based LEDs have been costly and difficult to produce on a wide-scale in an efficient manner. Although successful, solid state lighting techniques must be improved for full exploitation of their potential.